Control apparatus



J. W. DAWSON CONTROL APPARATUS Oct. 3, 1933.

2 Shee s-'-Sheet 1 Filed Dec 19, 1930 INVENTOR WITNESSES:

ATTORNEY Oct. 3, 1933. J. w. DAWSON CONTROL APPARATUS Filed Dec. 19,1930 2 Sheets-Sheet 2 m Fi /2 INVENTQR John WDawsan.

c I ATTORNEY Patented Oct. 3, 1933 CONTROL APPARATUS John W. Dawson,Wilkinsburg, Pa, assimor to Westinghouse Electric & ManufacturingCompany, a corporation of Pennsylvania Application December 19, 1930Serial No. 503,484

8 Claims.

My invention relates to control apparatus and has particular relation tocontrol apparatus of a type utilized in producing mechanicalreciprocating or rotary motion of a predetermined period.

It is an object of my invention to provide control apparatus capable ofdelivering an electromechanical force of predetermined periodicity.

Another object of my invention is to provide control apparatus capableof delivering a periodic force of uniform magnitude.

A further object of my invention is to provide control apparatus capableof delivering an electro-mechanical force, the magnitude of which shallvary with uniform periodicity.

A further and more specific object of my invention is to provide controlapparatus for operating a mechanical vibrator.

Another specific object of my invention is to provide apparatus forattaining a mechanical or electrical disturbance of predeterminedproperties from an electrical source having given properties.

An ancillary object of my invention is to provide, in control apparatusof a type incorporating an inductor, a device for preventing theinductor, by its electromagnetic action, from distorting the action ofthe control system proper.

Another ancillary object of my invention is to provide, in controlapparatus of a type including an inductor, a device whereby the energyaris ing from a current of predetermined polarity, established in theinductor, is rapidly dissipated, in an independent network providedtherefor.

A further ancillary object of my invention is to provide in controlapparatus of a type including a plurality of electric discharge tubes,that are periodically extinguished, and an inductor, a device wherebysaid inductor is prevented from influencing the condition of the tubes,by its magnetic action.

More concisely stated, it is an object of my invention to providevibratory apparatus of a type wherein the mechanical vibrator shall havea motion of uniform periodicity and of uniform amplitude.

According to my invention, I provide, for vi brating apparatus, acontrol system, for producing a periodic electro-magnetic force, of atype wherein the coil of an electromagnet is periodically excited by thecurrent traversing a grid controlled electric discharge tube. Thepotential of the grid of the tube is varied periodically by the actionof a commutator disc that coacts with a source of potential independentof the source provided for operating the tube. The periodicity and theamplitude of the force is maintained uniform by reason of the fact thatthe commutator is rotated in synchronism with the alternations in thepower source supplying the potentials for operating the tube.

According to a modification of my invention, the coil of theelectro-magnet is excited from a plurality of tubes connected inpush-pull relationship. By properly adjusting the number and theposition of the segments of the commutator associated with the tubes, anelectro-magnetic force of any predetermined characteristics may beproduced with apparatus of this type.

Finally, the back-electromotive-force, arising from a currentestablished in the coil of the elec- 7O tro-magnet, is prevented fromperceptibly distorting the character of the disturbance that isdelivered by the system by the action of a rectifier that is soconnected in the system as to shunt the coil. I have found that by theaddition of the rectifier, a rather aggravating fault has been remedied.

The novel features that I consider characteristic of my invention areset forth with particularity in the appended claims. The inventionitself, however, both as to its organization and its method ofoperation, togeth :r with additional objects and advantages thereof,will best be understood from the following description of specificembodiments, when read in connection with the 35 accompanying drawings,in which:

Figure 1 is a view in perspective showing a vibrating system to which myinvention has been specifically applied.

Fig. 2 is a view, partly in section and partly in elevation, taken onthe line 11-11 of Fig. 1, showing the principal motivating elements ofthe vibrator,

Fig. 3 is a view in vertical section of the upper structure of theapparatus shown in Fig. 1, Fig. 4 is a view in perspective illustratingcertain electrical and mechanical features of a commutator utilized inan embodiment of my invention,

Fig. 5 is a perspective view of the sector disc of a commutator disc ofa specific type,

Fig. 6 is a second perspective view showing certain additional elementsof the commutator disc,

Fig. '7 is a schematic view showing the electrical circuit of anembodiment of my invention,

Fig. 8 is a graph illustrating the action of the apparatus shown in Fig."I,

Fig. 9 is a schematic view showing a modification of my invention,

Fig. is a graph illustrating a characteristic of the apparatus shown inFig. 9, and

Figs. 11 and 12 are views illustrating further modifications of myinvention.

The apparatus shown in Figs. 1, 2 and 3 comprises a. plurality ofhorizontal supporting blocks '1, near one extremity of which, vertical.supporting blocks 3 are mounted, and near the other extremity of which,brackets 5 of substantially transverse C-section are mounted. A boredbracket 7 is supported on the upper end of each vertical block 3, andthe openings 9 in each bracket 7 are traversed by cylindricalprojections ll extending rrom a plate 13, supporting the upper end of anenclosure in which a siftingscreen l? is movably mounted.

The lower end or" the enclosure 15 is supported on a plurality oi studs19 that engage a. plurality of bosses 21 fastened to, or cast integralwith, the walls '23 of the enclosure. The studs 19 are supported betweenthe flanges 25 of the brackets 5, of r3-section, on a bolt 2? thattraverses circular openings in the flanges and an opening lower ends ofeach stud.

Toe projections ll extending from the plates supporting the upper end ofthe enclosure 15 r ble of rotating relative to the brackets t? .in whichthey are supported, while the studs 19, supporting the lower end. of theon closure l5, may be pivoted relative to the bolts fit, suporting them.region of engagement the To sses 21, projecting from the enclosure thestuds may be varied in a vertical ction and consequently the angularposition -e enclosure be adjusted in any predeterecl manner.

e mechanism utilized in producing the vi in the sitting screen i? ismounted on a plate 29 supported between the upper ends 31 of enclosure15. comprises a chamber in which fastened the core 35 and the odings 3?of an electro-znagnet 39. The electrc-magnet 39 is adapted to beexcited, as shall explained hereinafter, and when excited, its core 35attracts a movable armature il that is resiliently supported, adjacentthereto, between a plurality of compression springs 43 and i5.

stud 47 projects from the lower surface of he bracket 49, to which thearmature ll is astened, and has mounted on its lower end, a ulurality oflegs 51 that are fastened to a rod 53 which is in turn rigidly securedto the sifting screen 17. As the armature ll moves under the ction ofthe electrounagnet 39 and the springs the screen 1? is in turnmotivated.

end of one spring l3 between which cure floats, engages a groove 55lower surface of a cylndrical shell on lower end of a threaded stud westud 5Q projects from a cylindrical extension or" the chamber 33 whereinthe electro-rnagnct 39 and armature c1 are mounted. The upper end of thestud 59 has fastened thereto a hand-wheel 63 whereby the stud may berotated relative to the tapped opening 65 in the extension 61 from whichit projects. The vertical position of the upper end of the spring 43,and hence the vertical position of the armature 41, may thus beregulated, and as a result the amplitude of vibration oi thesifting-screen 17 may be adjusted. The stud 59 is, of course, locked inany one of its vertical positions.

The electrical circuit or" a system, whereby the excitation of theelectro-magnet 39 is produced, is illustrated in Fig. 7. The apparatus@9 prises an electric discharge tube 67, (preferably a grid-control gasdischarge or g ow tube), the principal electrodes 69 and 71 of which areconnected to the terminals of the coil 3'7 01' the electro-magnet 39,and the power for the operation of which is supplied from an alternatingcurrent source 73.

The control electrode 75 or the tube 67 is connected through a brush'76, to the shaft '7'? that supports a conducting disc 'IQ provided withan insulator sector 81 and rotated through a. system of gears 83 from asynchronous motor 85. The power for the motor 851s supplied from thesame source 73 as supplies the potential between the anode 69 and thecathode 71 of the tube 67.

The disc '29 is engaged by a plurality of fixed brushes 8'? that areconnected to the terminals $39 and 90 of a split power supply source 91such as a battery. The remaining terminal 92 of the source 91 isconnected to the anode 69 of the tube 67.

As the disc 79 rotates, a voltage of predetermined magnitude and ofpredetermined polarity is impressed on the grid 75 of the tube 67, andas a result the condition of the electric discharge in the tube 3? isvaried. In apparatus or the type illustrated in Fig. i, the grid '15 ofthe tube 6*! is alternately adjusted to negative and positive potentialsrelative to the anode the tube is alternately in an unexcited and anexcited state, respectively. The electro-magnet 39 in turn responds tothe condition oi the tube 67 causes the screen to be reciprocatedaocordi' gly.

is ustrated in ."Jig. i, the electric tube 5*"? is of the hot cathodetype. i is understood that plural electrode tubes the coldcathode typeare also useable in reciprocating systems of the type described herein.liowever, where a comparatively heavy current is utilized, it preferablethat the tubes he of the hot cathode type and for the heaviest dutygridcontrolled mercury pool cathode tubes are preferabie.

The cathode ll oi? the tube requires considerable time to be heated to aproper temperature for emitting, and it is seriously impaired if itemits before it reaches this temperature. A time delay relay 93 istherefore provided for preventing the application of the requisitepotential between the anode G9 and the cathode ll of the tube 6'? untilthe cathode has attained a proper temperature.

Furthermore, it is understood the potentials applied to the grid 75 bythe contact disc '"!9 must be properly related polarity to thepotentials applied between the principal electrodes 69 and ll. of thetube 6'? for satisfactory operation of the system. t is to be noted thatthe proper current is not passed by the tube 67 if the grid 75v isnegative polarity relative to the anode so at the beginning of eachcycle of operation of the disc 79.

The coil 94 of relay equipped with a contactor 96 that is adapted toregulate the activity of the motor circuit, is therefore included in theprincipal circuit oi the tube 67. The contactor 96 is in parallel withthe contactor 97 of the time delay relay 93 and when the latter closesthe motor circuit is open unless the tube 67 is passing sufflcientcurrent. That is to say, power is not supplied to the motor 85 unlessthe disc 79 is propdischarge crly oriented in phase. relative to thealternations of voltage impressed between the principal electrodes ofthe tube 67.

Initially the motor 85 is started through the contactor 97 of the relay93 which is in engagement with the lower fixed contacts of the relaywhen power is applied. When the cathode 71 is properly excited and therelay 93 is energized, the motor 85 can only be energized through thecontactor 96 of the relay 95. If the disc 79 is so oriented at any timethat the device 67 remains deenergized for an appreciable interval, therelay 95 is deenergized. When the supply of energy to the motor is thusstopped, its speed decreases and, in coasting the disc, necessarilypasses through a condition in which the device 67 becomes energized andthe relay 95 receives an impulse to energize it. It is evident that atthe time that the relay 95 receives the energizing impulse the rotor ofthe motor 85 may be moving so slowly that it is pulled into proper stepby the engagement of the contactor 96 with its corresponding fixedcontacts regardless of how sluggish the relay 95 is. However, in thepreferred practice of my invention the relay 95 is a rather quick actingrelay.

It is well to point out that the relays 93 and 95 have not been shown inthe modified systems illustrated in Figs. 9, 11 and 12. However, theyhave not been incorporated in the viewsfor purposes of clarity. Theirincorporation in the actual systems of the type shown in Figs. '7, 9, 11and 12 will be apparent to one skilled in the art and the relay systemsare, as a matter of fact, generally incorporated in actual apparatus ofthis type.

Finally, it is apparent that if tubes of the cold electrode type areutilized the time delay relay 93 is not necessary. The circuit is thenslightly modified.

It is to be noted that as illustrated in Fig. 7, the restoring force forthe screen 17 is provided by a tension spring 98 instead of twocompression springs as is illustrated in Figs. 1, 2 and 3. This featureof the illustration should only be regarded as symbolical.

In Fig. 8, the action of the system shown in Fig. 7 is illustratedgraphically. The shaded areas 99 under the curve 101 of comparativelysmall amplitude, represent the periods during which current is flowingthrough the tube 67. The curve 103, of large amplitude, indicates theposition of the screen 17. The values of positive ordinate, representits position as it approaches the magnet 39, and the values of negativeordinate represent its position as it retracts from the magnet. Thepotentials 39 and 90 of the grid are designated below the axis ofordinates on the raph.

As can be seen from the graph, according to my invention, I provide,essentially, a device whereby a mechanical frequency of a predeterminedperiod is attained from an electrical frequency of given period. In theparticular case illustrated in the graph, the mechanical frequency is /3of the electrical frequency. Thus, a frequency of cycles, which isordinarily available, yields a mechanical frequency of 20 cycles.

It is, furthermore, to be noted that by synchronizing the rotation ofthe sectored disc 79 with the alternations of the power supplied to thetube 67, I am able to obtain a condition wherein the oscillations of themechanical vibrator 17 are uniform in period and magnitude.

Apparatus of the type illustrated in Fig. 7 may be utilized to attain amechanical motive vibration comparatively simple in character. Modes ofvibration of more complicated character may be attained with apparatusof the type illustrated in Fig. 9.

The apparatus illustrated in this view comprises a plurality of tubes105 and 107, herein shown as hot-cathode grid-glow tubes, the anodes 109and 111 of which are connected to two terminals 113 and 114 of apower-transmission transformer 115 and the cathodes 117 and 119 of whichare connected to a shaft 121 whereon a commutator 123, of apredetermined character, is mounted.

The grids 125 and 127 of the tubes 105 and 107 are connected to brushes129 and 131 that are adapted to make contact with the segments 133 and135 of thg rotating commutator 123 through power sources 137 and 139 ofsuitable electrical character. The exciting coil 37 of the electromagnet39 is connected between the electrical center 141 of the secondary 143of the transformer 115, whereby power is supplied to the tubes 105 and107, and the common electrical center 145 of the secondary 147 of thetransformer 149, whereby power is supplied for heating the cathodes 117and 119 of the tubes.

As is illustrated in the view, a negative bias is impressed on the grid125 or the grid 127 of a tube 105 or a tube 107, when the brush 129 orthe brush'131 associated therewith makes contact with the conductingelement 133 of the commutator disc 123, and, correspondingly, the gridis insulated when the brush makes contact with the insulating segment135 of the commutator. In the latter case, the corresponding tube breaksdown and a current passes through the exciting coil of the magnet.

It is seen that the condition produced in the electrc-magnet isdetermined by the angle between the brushes 129 and 131 and by theangles subtended by the insulating and the conducting segments 133 and135 of the commutator disc 123.

It has long been known that the passage of a current through an inductorcauses a magnetic flux to be set up in the region associated therewith.When the current is decreased the flux decreases in turn, causing thecurrent to maintain itself.

In the present connection, the persisting current tends to produce anelectromotive force between the principal electrodes of the tubes 105and 107 which in turn tends to maintain the tubes in a state ofexcitation. Consequently, the character of the mechanical vibrationsthat the system yields is distorted.

I have found that this undesirable condition may be eliminated by theaddition of a rectifier 151 shunting the coil 37 of the electro-magnet39 and of such polarity that the persisting current from the coil isdissipated in its circuit, and does not pass through the tubes 105 and107. It is to be noted that when the current through the coil 37decreases, the voltage across the rectifier is in such a direction as tocause it to pass current.

In Fig. 10 the curve 153, wholly above the axis of abscissae,illustrates the condition that is attained in the tubes when theshunting rectifier 151 is not present in the circuit, and the lowercurve 154 illustrates the condition when the rectifier 151 is added tothe circuit. If the discharge rectifier 151 is included in the circuit,the excess energy represented by the shaded area in Fig. 10 isdissipated therein. The ordinates of the control-electrodes oi! saiddevices to alternately vary the state of excitation of said devices.

5. In apparatus for transforming an electromotive force of givencharacteristics of frequency and amplitude into an electro-motive-iorceof predetermined characteristics of the type including a commutatordisc, a source of power associated with said disc, and a plurality ofelectric discharge devices, said electric discharge devices comprising aplurality of principal electrodes, and a control electrode, thepotentials of said principal electrodes being applied from said givenelectro-motive force, and the potentials of said control electrodesbeing applied through said commutator disc from said source of powerasso-. ciated therewith, means for controlling the phaserelation of thepotentials applied between said principal electrodes and the potentialsapplied to said control electrodes.

6. Control apparatus comprising energy translating means, at least oneelectric discharge device incorporating a control electrode and aplurality of principal electrodes for transmitting power to saidtranslating means, alternating power supply means for impressing anelectromotive force between the principal electrodes of said electricdischarge device, means operating in synchronism with said power supplymeans for alternately applying a distribution 01' potential between saidcontrol electrode and said principal electrodes to maintain saidelectric discharge device deenergized and another distribution ofpotential between said control electrodes and said principal electrodesto energize said electric discharge device, and means responsive to thecurrent transmitted by said electric discharge device to maintain saidpotential-distribution-varying means in synchronism with said powersupply means.

'7. Control apparatus comprising an inductor, power supply means, meansincluding an electric discharge device, having an energized and adeenergized condition, connected to said inductor and to said powersupply means for transmitting periodic unidirectional current impulsestherethrough, and an asymmetric network connected to said inductor insuch manner as to be non-conductive to the unidirectional currenttransmitted through said inductor and conductive to a current in thedirection of the electromotive iorce built up by the collapse of theflux in said inductor during the intervals between pulses ofunidirectional current, for shunting out said electric discharge deviceduring these intervals.

8. In control apparatus of the type incorporating an inductor, powersupply means, means including an electric discharge device having anenergized and a deenergized condition, coupled to said inductor and tosaid power supply means for

